BTK and B-cell chronic lymphocytic leukemia: Regarding mutation detection in ibr-relapsed patients, implications of our discovery are two-fold: 1) For management of ibr relapsed/resistant CLL, mutation detection of BTK should include all exons, not just those encoding the kinase domain; and 2) The possibility of a minute mutant clone evolving during ibr treatment entails a highly sensitive technique for clinical early detection.